Studies proposed in this research project are concerned with the mechanism by which ions, hormones and secondary cytoplasmic factors control and mediate oocyte differentiation processes (growth, maturation and activation). We have recently identified, in progesterone treated amphibian oocytes, a biologically active cytoplasmic material which inhibits transport of the yolk protein precursor (3H-vitellogenin) across the oocyte cell membrane when injected into non-hormone treated oocytes. Particularly, we wish to: (1) isolate and characterize this inhibitory factor, (2) establish whether it is the same or different from other biologically active cytoplasmic factors also present in hormone treated oocytes, (3) elucidate how the inhibitor is formed in the oocyte and how it acts on the cell membrane. (4) In addition, we wish to determine if oocytes of other species in which the same stages of meiotic differentiation are controlled by different hormones or factors, contain similar biologically active cytoplasmic factors as those found in amphibian oocytes. The involvement of calcium and other ions in the process of differentiation will also be studied. The role of ions in the process of mammalian oocyte maturation will be tested by directly altering the intra- and extrafollicular microenvironment of cultured follicles. The ionic composition of the follicular fluid will be analyzed during the course of induced maturation in vitro. Oocytes at different stages of in vitro differentiation will be analyzed to determine if there are (1) quantitative changes in the amount of bound and unbound calcium in the oocyte as determined by atomic absorption spectrophotometry, (2) alterations in calcium45 incorporation, (3) changes in the binding capacity of oocytes microinjected with Ca45. The role of calcium and cytoplasmic factors on propagation of maturation and activation responses within the oocyte will be examined.